Title: Combining bioavailability assays with modeling to predict PCBs in fish after remediation Project summary Ecological and human health impacts of bioaccumulative contaminants like PCBs are primarily manifested through accumulation of the toxic compounds in higher trophic level organisms like fish that are consumed by humans and top predators in the ecosystem. However, changes in fish are slow to manifest as a consequence of a remedial action and often one has to wait for several years to see such change. To make timely assessments of remediation progress, one alternative is to perform appropriate measurements that indicate changes in key pathways of exposure to fish. Although some advances have been made recently to assess porewater concentrations using passive sampling techniques which respond more rapidly to in-situ remedies, relationship of such measures to accumulation is fish has not been demonstrated. Also, there is a major gap in the development and utilization of fate and biouptake models that can use passive sampling measurements and quantitatively link those measurements to uptake pathways and predict eventual changes in fish concentrations. This proposed research project will refine sampling methods to assess PCB uptake pathways and work with practitioners to incorporate such measures into PCB fate and biouptake models to assess changes in fish concentration over time, and validate the approach through controlled laboratory exposure studies and measurements in the field. The three primary aims of this project are: Specific aim 1: Develop the fundamental basis of passive sampling. This research will use advanced fluorescence microscopy, IR microspectroscopy, and sectioning techniques to directly measure the diffusion of organic molecules in commonly used passive sampler materials (polyethylene, polyoxymethylene, and PDMS). This effort will lead to the selection and use of appropriate polymeric materials for passive equilibrium sampling with much greater confidence about the nature of equilibrium achieved during the exposure period. Specific aim 2: Use passive sampling to measure bioavailability processes and uptake in fish. This research aim will evaluate how sediments amended with activated carbon sorbents in the field impact PCB biouptake in two types of fish through controlled laboratory mesocosm studies and compare with uptake in passive sampling devices developed under Aim 1. Specific aim 3: Incorporate passive sampling inputs to PCB fate and bioaccumulation model. A mathematical model will be developed and used to interpret results from: 1) the mesocosm exposure experiments, and 2) field observations from a PCB-impacted river site to explore the effect of activated carbon treatments on PCB accumulation in fish. Of particular interest is improving the accuracy of model predictions of the benefits of in-situ treatment with activated carbon aimed at reducing pore water concentrations and contaminant bioavailability.